Bmesh.ops.mesh_to_bmesh usage returns cryptic error
The proper function to be used is the  bm.from_mesh(me) function where bm is the bmesh object being transferred to and me is the mesh. Also for the reverse operation we can use bm.to_mesh(me) which will load the bmesh data back into the mesh.

For code example see the template bmesh_simple.py which is included in blender text editor.



some of the bmesh operation didn't work yet like bmesh.ops.bmesh_to_mesh , mesh.ops.mesh_to_bmesh and bmesh.ops.object_load_bmesh, the only note is that the DOC says :     


  this bmop is private